This invention relates to integrated circuit modules of the kind which include pressed electrical connections between two components.
In the prior art, an example of an integrated circuit module that uses pressed electrical connections is disclosed in U.S. Pat. No. 4,999,023 which is entitled "High Density Low Reactance Socket". There, in FIGS. 2A and 2B, a compressible contact is indicated by reference numeral 15. This contact 15 is comprised of a wad of wire that is held by a sleeve 14.
In FIGS. 2A and 2B of patent '023, each contact 15 makes a pressed electrical connection between an input/output pin on a packaged integrated circuit chip and a signal line in a printed circuit board. This electrical connection is made by inserting the input/output pin into the sleeve 14 and pushing against the contact 15. By utilizing such a pressed electrical connection instead of a soldered connection, the packaged integrated circuit chip can easily be removed from the printed circuit board and replaced with another packaged chip.
Each contact 15 which is compressed exerts an opposing force against the input/output pins on the printed circuit board. Thus, as the total number of pressed electrical connections increases, the total opposing force which is exerted against the input/output pins and the printed circuit board also increases.
As a numerical example, suppose that there are a total of 1,000 pressed electrical connections between the packaged integrated circuit chip and the printed circuit board, and that each pressed connection exerts an opposing force of 2 ounces. For that case, the total opposing force against the input/output pins and the printed circuit board is over 100 pounds.
By increasing the total opposing force with which all of the pressed electrical connections exert against the input/output pins and the printed circuit board, a point is eventually reached where the printed circuit board will deflect and bend. Due to that bending, mechanical stress is generated in the printed circuit board; and this stress can damage the board. Also, if the printed circuit board is bent, then all of the compressible contacts do not get compressed by the same amount; and, a contact which is compressed too little can act as an open circuit or high resistance connection.
To keep the maximum deflection of the printed circuit board within an acceptable limit, a stiff-flat plate can be bolted to the printed circuit board. However, in order for a flat plate to be stiff, the plate needs to be thick; and that increases the profile of the module. Increasing the profile is undesirable because that reduces the spacing with which multiple printed circuit boards can be placed side-by-side in an end product.
Accordingly, a primary object of the present invention is to provide an improved electromechanical module which makes pressed electrical connections between an integrated circuit chip package and a printed circuit board in a novel fashion such that deflection and stress in the printed circuit board are kept low without significantly increasing the profile of the module.